1. Field of the Invention
The present invention relates to a technique of calculating the rotation angle of a motor by means of a multipole resolver.
2. Description of the Background Art
Conventionally, a technique of detecting or calculating, by means of a resolver, the rotation angle of a motor which is mounted on a hybrid vehicle, electric vehicle or the like has been known. The resolver is attached to the rotating shaft of the motor, and generates an electrical signal (analog signal) in accordance with the rotation angle of the motor, based on a change in magnetic flux. The electrical signal generated by the resolver is converted into an angular signal (digital signal) by a resolver-to-digital conversion circuit. While the torque of the motor is controlled based on the angular signal, it is known that this angular signal involves an error. With the purpose of improving accuracy in control of the motor, various techniques have therefore been proposed for correcting and thereby eliminating the error involved in the angular signal.
For example, Japanese Patent Laying-Open No. 2010-96708 (Patent Document 1) discloses a technique as follows. In the case where the rotation angle of a motor is to be calculated with a multipole resolver, one period taken for the motor to make one full rotation is equally divided into n sections in accordance with the number of poles (shaft angle multiplier) n of the resolver, it is determined in which of the n sections the angle detected by the resolver is included, and an error of the detected angle is individually corrected for each section. With this technique, even if respective detection errors generated in the n sections are different from each other, the errors are corrected individually section by section, and therefore, the correction of the errors can be made accurately.